Immiscible nanostructured copper-aluminum-niobium alloy with excellent precipitation strengthening upon friction stir processing and aging

Abstract

Abstract A ternary immiscible nanostructured Cu-Al-Nb alloy was fabricated by friction stir processing of mechanically compacted pellets. Subsequently, aging was carried out at 563\u202fK for various times. The material exhibited hardness of ~4.3\u202f±\u202f0.1\u202fGPa in the peak-aged condition (aging for 6\u202fh), which is remarkable among Cu-based ternary immiscible alloys. The excellent strength of the material is attributed to Hall-Petch strengthening due to the extremely refined nanocrystalline structure, coupled with precipitation strengthening due to a uniform distribution of nano-scale Al- and Nb-rich precipitates or clusters, as confirmed by X-ray diffraction and microstructural characterization.